Recent research suggests that cerebral damage occurs in cocaine abusers. The primary goals of this project are: a) to study the cerebral metabolic, neuronal, and blood flow effects of chronic cocaine abuse, b) to compare and contrast these effects with those of chronic alcohol abuse, and c) to determine whether there are synergistic effects of cojoint cocaine and alcohol abuse (cojoint abuse of cocaine and alcohol is highly prevalent and there are reasons to believe that it may produce an increased risk of toxicity). The secondary goals are to determine if these cerebral metabolic, neuronal, and blood flow effects are transient or relatively permanent, and to determine whether these effects differ in males and females. To accomplish these goals, we will use 1H and 31P magnetic resonance spectroscopic imaging (MRSI), single photon emission computed tomography (SPECT), and magnetic resonance imaging (MRI) to study four samples of African American subjects: cocaine-only abusers, alcohol-only abusers, cocaine-alcohol abusers and non-substance abusing controls. Each sample will consist of half males and half females. Our pilot work, using single volume 31P MRS, demonstrated reduced phospholipid metabolite concentrations in the white matter of cocaine abusers compared to normal controls and replicated SPECT findings of cerebral perfusion in cocaine abusers. Recent MRS developments now allow us: (1) to use 1H MRS to investigate neuron loss and neuronal viability by measuring N-acetyl aspartate (NAA), and (2) to use MRSI to study MR observable 1H and 31P metabolites through the brain, including in the regions demonstrating perfusion defects on SPECT.